Zoom lens system

ABSTRACT

An eight component afocal zoom system is provided characterized by extremely short length considering the zoom range and its field and aperture size. A substantially flat image field is obtained through a zoom range of substantially to 2.54.

0 United St: 1111 3,790,255 Shoemaker X (/0 4/ 1451 Feb. 5, 1974 ZOOM LENS SYSTEM 3,030,861 4/1962 Mortimer et a] 350/184 [75] Inventor: Arthur H. Shoemaker, E. Aurora,

Primary Examiner-John K. Corbin [73] Assignee; American Optical Corporation, Altorney, Agent, or Firm-Alan H. Spencer; William Southbridge, Mass. C. Nealon [22] Filed: Sept. 11, 1972 [2]] Appl. No.: 288,231 [57] ABSTRACT [52] US. Cl 350/184, 350/176, 350/2l4 A i ht onent afocal zoom system is provided [51] Int. Cl. characterized by extremely hort length considering Of Search the oom range and and aperture size A substantially flat image field is obtained through a zoom [56] R er c Cited range of substantially to 2.54.

UNITED STATES PATENTS 3,640,605 2/1972 Sissel 350/184 3 Claims, 1 Drawing Figure PARALLEL L/GH T ZOOM LENS SYSTEM BACKGROUND OF THE INVENTION The present invention relates to afocal optical devices for obtaining from a given object at infinity, a well corrected image which remains substantially fixed, although the angular size of the image may be progressively varied between two predetermined limits by a suitable displacement of a number of the elements of the device.

OBJECTS OF THE INVENTION It is an object of this invention to provide an optical device well suited for use as a zoom attachment to an infinity corrected microscope system whose image, as well as being well corrected for the usual chromatic aberrations, spherical aberrations, coma, and astigmatism, has a substantially flat image field throughout a zoom range of substantially l to 2.5X

DRAWING The drawing is an optical diagram of a zoom optical system according to the present invention.

DESCRIPTION The drawing is an optical diagram of the preferred form of the present invention wherein the numeral X designates the system in general. The system is comprised of a front stationary lens group, group XI, spaced away from the entrance pupil surface 20 at a distance designated 81. Rearward of, and optically aligned with XI, are the two zoom groups, groups XII and XIII respectively whose variable spaces are designated S3 and S6. The zoom groups serve to vary the angular subtense of the object.

The system is comprised of eight optically aligned components designated A, B, C, D, E, F, G, and H respectively. Group XI is comprised of a positive double convex doublet, component A, and a concavo convex negative singlet, component B. Group XII is comprised of component C, a negative double convex singlet; component D, a convex concavo negative singlet; and component E, a negative double convex doublet. Finally, group XIII is comprised of a concavo convex positive doublet, component F; a double convex positive singlet, component G; and a double concave negative singlet, component H.

The successive air spaces of the system are designated S1 to S8 respectively, while successive axial lens thicknesses are designated T1 to T1]. Successive radii of curvature are designated R1 to R19 respectively where the minus sign applies to surfaces whose center of curvature lies on the entrance pupil side of their vertices. The refractive indices and Abbe numbers of the glasses in the successive lenses are designated ND (1) to ND (11) and v (I) to v (11) respectively.

In the table below a list of the lens parameters is given in terms of L, the over-all length of the system at the 1X position (see the drawing).

Radius Thickness Space Refractive Ahhe R 'l' S Index Number ND 11 S l =().())27L Numerically stated, the constructional data for one Tl l=2.390 NDl l=l.48749 ul l=70.-

Having thus described the invention in detail and with sufficient particularlity to enable those skilled in the art to practice it, what is desired to have protected by Letters Patent is set forth in the following claims.

What is claimed is:

1. An afocal optical lens system of the zoom type having an extremely short length and a range for use with an infinity correcting microscope system in which the image, as well as being well corrected for chromatic abberations, coma, and astigmatism, has a substantially flat image field through a zoom range of substantially l to 2.5x, said system comprised of three sets of lenses, Xl, Xll, and Xlll;

Xl being comprised of a positive convex doublet consisting of a double convex lens cemented to a concave convex negative lens, and a second concave convex negative lens;

Xll is comprised of a negative double concave singlet, a convex concavo negative singlet and a negative double concave doublet, said doublet comprised of a concave convex positive element cemented to a double concave lens element; and

X11] comprised of a concavo convex positive doublet comprised of two concavo convex singlets cemented to each other, a double convex positive singlet and a double concave negative singlet.

2. The zoom lens arrangement of claim 1 in which the parameters of lens radii .(R), thicknesses (T), and spacings (S) are expressed in millimeters and a negative sign indicates lens radii on centers of curvature on the object side of the lens R l 6=0.3880L Ahhc Number vlO=49.-

3. The zoom system of claim 2 in which L 75.48

millimeters. 

1. An afocal optical lens system of the zoom type having an extremely short length and a range for use with an infinity correcting microscope system in which the image, as well as being well corrected for chromatic abberations, coma, and astigmatism, has a substantially flat image field through a zoom range of substantially 1 to 2.5X, said system comprised of three sets of lenses, XI, XII, and XIII; XI being comprised of a positive convex doublet consisting of a double convex lens cemented to a concave convex negative lens, and a second concave convex negative lens; XII is comprised of a negative double concave singlet, a convex concavo negative singlet and a negative double concave doublet, said doublet comprised of a concave convex positive element cemented to a double concave lens element; and XIII comprised of a concavo convex positive doublet comprised of two concavo convex singlets cemented to each other, a double convex positive singlet and a double concave negative singlet.
 2. The zoom lens arrangement of claim 1 in which the parameters of lens radii (R), thicknesses (T), and spacings (S) are expressed in millimeters and a negative sign indicates lens radii on centers of curvature on the object side of the lens Radius Thickness Space Refractive Abbe R T S Index Number ND Nu S1 0.0927L R1 0.3154L T1 0.0397L ND1 1.51821 Nu 1 65.10 R2 -0.2636L T2 0.0199L ND2 1.80518 Nu 2 25.43 R3 -0.3885L S2 0.0751L R4 -0.3324L T3 0.199L ND3 1.78847 Nu 3 50.48 R5 -0.8341L (1.0X) S3 0.559L (1.7X) S3 0.1317L (2.5X) S3 0.1664L R6 -1.1806L T4 0.0187L ND4 1.51821 Nu 4 65.10 R7 0.3284L S4 0.0227L R8 0.1644LT5 0.0368L ND5 1.80518 Nu 5 25.43 R9 0.1644L S5 0.0258L R10 -0.4546L T6 0.0275L ND6 1.80518 Nu 6 25.43 R11 -0.1422L T7 0.0205L ND7 1.78847 Nu 7 50.48 R12 0.4384L (1.0X) S6 0.2961L (1.7X) S6 0.1675L (2.5X) S6 0.0203L R13 -7.9799L T8 0.1003L ND8 1.78847 Nu 8 50.48 R14 -0.2443L T9 0.0311L ND9 1.80518 Nu 9 25.43 R15 -0.6294L S7 0.0037L R16 0.3880L T10 0.0572L ND10 1.61772 Nu 10 49.78 R17 -1.7885L S8 0.0247L R18 -1.0210L T11 0.0317L ND11 1.48749 Nu 11 70.45 R19 0.3283L
 3. The zoom system of claim 2 in which L 75.48 millimeters. 